Bending threshold and release for a flexible display device

ABSTRACT

A flexible display device and method for detecting a bend on the device are discussed. The method includes detecting a first bend on the flexible display device and measuring a first degree of the first bend; recognizing the first bend as a first valid flex input when the measured first degree of bend surpasses a first error threshold value; and recognizing an end of the first valid flex input when the measured first degree of bend falls below a first release threshold value, wherein a maximum degree of bend measured during the first bend is recognized as a first peak value, wherein the first error threshold value is determined based on a degree before the flexible display device is bent and the first release threshold value is determined based on the first peak value, and wherein the first release threshold value is different from the first error threshold value.

This application is a Continuation of co-pending application Ser. No.13/407,791 filed Feb. 29, 2012, which claims the benefit of U.S.Provisional Application No. 61/581,646 filed on Dec. 30, 2011, theentire contents of all of the above applications are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

With the continued advancements in mobile device technology, mobiledevices are able to offer greater processing power and capabilities. Forinstance, smart phone type mobile devices allow a user to connect to theinternet, check emails, shop online, receive news updates in real-time,look up real-time traffic conditions and generally connect to otherusers throughout the world. As a result of the increased capabilities ofmobile devices, these mobile devices are becoming an integral part of aperson's everyday life.

Following the introduction of touch sensitive display screens on mobiledevices, users have come to experience a whole new way of interactingwith their mobile device. Whereas prior to the introduction of touchsensitive display screens a user was limited to interacting with theirmobile device solely though hard wired buttons, with the introduction oftouch sensitive display screens users are able to directly interact withobjects displayed on the display screen. The user experience of having atouch sensitive display screen is vastly popular amongst consumers, andsome may even consider such technology to be a must have option for anymobile device they are to buy. So more and more, consumers are lookingfor the latest technology that can provide a new and exciting userexperience.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a flexible displaydevice that allows a user to interact with the flexible display deviceby physically bending the body of the flexible display device. Eachbending input made by a user may be recognized by the flexible displaydevice as a specific command for controlling a feature of the flexibledisplay device. By allowing a user to input commands on the flexibledisplay device by physically deforming the body of the flexible displaydevice, the present invention offers a new and unique user experiencenot offered by non-deformable display devices.

Now in order for the flexible display device to accurately recognize auser's bending of the body as a valid input command, the flexibledisplay device must be able to distinguish unintentional bends on thebody from intentional bends by the user. It is therefore an object ofthe present invention to provide a solution for distinguishingunintentional bends on the body of a flexible display device fromintentional bends on the body of a flexible display device.

It is further an object of the present invention to provide a solutionfor accurately identifying a starting point for an intentional bendingcommand input and an ending point for an intentional bending commandinput. By offering the following solutions described throughout thisdescription the present invention is able to substantially resolve thelimitations and deficiencies of the related art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block diagram describing components of a flexibledisplay device, according to the present invention;

FIG. 2 illustrates a first method of bending a flexible display device,according to the present invention;

FIG. 3 illustrates a second method of bending a flexible display device,according to the present invention;

FIG. 4 illustrates a graph plotting a measured degree of bending on aflexible display device versus time for a single flex input, accordingto the present invention;

FIG. 5 illustrates a plurality of graphs, where each graph represents aseparate single flex input having varying maximum degrees of detectedbending, according to the present invention;

FIG. 6 illustrates a graph plotting a measured degree of bending on aflexible display device versus time for a double flex input, accordingto the present invention;

FIG. 7 illustrates a graph plotting a measured degree of bending on aflexible display device versus time for two successive single flexinputs, according to the present invention;

FIG. 8A illustrates a flowchart describing the steps of recognizing abeginning and end to a valid flex input, according to the presentinvention;

FIG. 8B illustrates a flowchart describing the steps of recognizing adouble flex input, according to some embodiments of the presentinvention; and

FIG. 8C illustrates a flowchart describing the steps of recognizing adouble flex input, according to some embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. It will be apparent to one of ordinary skill in the art thatin certain instances of the following description, the present inventionis described without the specific details of conventional details inorder to avoid unnecessarily distracting from the present invention.Wherever possible, like reference designations will be used throughoutthe drawings to refer to the same or similar parts. It is noted thatthroughout the description, any use of “flex” and “bend” will be usedinterchangeably to generally describe a flex or bend in a flexibledisplay device of the present invention.

FIG. 1 illustrates a general architecture block diagram for a flexibledisplay device 100 according to some embodiments of the presentinvention. The flexible display device 100 illustrated in FIG. 1 may,for example, be a mobile telecommunications device, notebook computer,tablet computing device or personal digital assistant (PDA). It is to beappreciated that it is within the scope of the present invention toutilize flexible display devices that may include a fewer, or greater,number of components than what is expressly illustrated in FIG. 1.

As illustrated in FIG. 1, the flexible display device 100 includes asystem controller 110, a storage unit 120, a communications unit 130, aflexible display unit 140, a sensor unit 150, an audio input output(I/O) unit 160 and a power unit 170. Although not all specificallyillustrated in FIG. 1, components of the flexible display device 100 areable to communicate with each other via one or more communication busesor signal lines. It should be appreciated that the components of theflexible display device 100 may be implemented as hardware, software, ora combination of both hardware and software.

The storage unit 120 may include non-volatile type memory such asnon-volatile random-access memory (NVRAM) or electrically erasableprogrammable read-only memory (EEPROM), commonly referred to as flashmemory. The storage unit 120 may also include other forms of high speedrandom access memory such as dynamic random-access memory (DRAM) andstatic random-access memory (SRAM), or may include a magnetic hard diskdrive (HDD). In cases where the flexible display device is a mobiledevice, the storage unit 120 may additionally include a subscriberidentity module (SIM) card for storing a user's profile information.

The storage unit 120 is tasked with storing various data andapplications that are needed to operate the flexible display device andprovide a user interface (UI). For instance, the storage unit 120 maystore software that describes a user interface allowing a user tointeract with the flexible display device 100 according to the methodsprovided by the present invention. In addition, applications stored onthe storage unit 120 may be a set of instructions that are processed bythe system controller 110 in order to execute and run the application.

In some embodiments of the present invention, the storage unit 120 mayfurther include access to remote storage in a cloud storage computingenvironment. The remote storage may be accessed via the communicationsunit 130.

The communications unit 130, as illustrated in FIG. 1, may include RFcircuitry that allows access to outside communications networks such asthe Internet, Local Area Networks (LANs), Wide Area Networks (WANs) andthe like. The wireless communications networks accessed by thecommunications unit 130 may follow various communications standards andprotocols including, but not limited to, Global System for MobileCommunications (GSM), Enhanced Data GSM Environment (EDGE), codedivision multiple access (CDMA), wideband code division multiple access(W-CDMA), time division multiple access (TDMA), Bluetooth, WirelessFidelity (Wi-Fi), Short Message Service (SMS) text messaging and anyother relevant communications standard or protocol that allows forwireless communication by the flexible display device 100. In someembodiments of the present invention, the communications unit may alsoinclude a tuner for allowing for the reception of broadcast signalsaccording to, for example, the digital multimedia broadcasting (DMB),digital video broadcasting technologies, advanced television systemscommittee (ATSC), integrated services digital broadcasting (ISDB) ordigital terrestrial multimedia broadcast (DTMB) standards.

Additionally, the communications unit 130 may include various input andoutput interfaces (not shown) for allowing wired data transfercommunication between the flexible display device 100 and an externalelectronics device. The interfaces may include, for example, interfacesthat allow for data transfers according to the family of universalserial bus (USB) standards, the family of IEEE 1394 standards or othersimilar standards that relate to data transfer.

The flexible display unit 140 illustrated in FIG. 1 includes a flexibledisplay that is preferably made from liquid crystal diode (LCD) displaytechnology, organic light emitting diode (OLED) display technology,electroluminescent display (ELD) technology or other similar flexibledisplay technologies. The flexible display unit 140 provides a visualoutput to a user for interacting with a user interface of the flexibledisplay device 100. The visual output displayed on the flexible displaymay include text, graphics, video and any combination thereof. One ofthe means a user may interact with the flexible display device 100 isvia a user interface that is displayed on a flexible display of theflexible display unit 140. Such a user interface may be comprisedprimary of text, graphics and video related to applications stored onthe storage unit 120.

The flexible display unit 140 illustrated in FIG. 1 may additionallyinclude a touch sensitive subsystem that comprises circuitry forallowing the flexible display 140 to be touch sensitive. The touchsensitive subsystem allows a user to interact with a user interfacedisplayed on the flexible display via touch inputs made on the flexibledisplay. Touch inputs detected by the touch sensitive subsystem aretransmitted to the system controller 110 for processing. According tothe present invention the detection of multi-touch inputs is supported,such that a multi-touch touch input may be detected by the touchsensitive subsystem and recognized by the system controller 110 as amulti-touch input.

The sensor unit 150, illustrated in FIG. 1, may include a plurality offlex sensors that are able to detect a location of a bend on theflexible display device 100 resulting from a user's bending of theflexible display device 100. Additionally, the flex sensors may alsodetect a degree of bend made on the flexible display device 100resulting from a user's flex input. In other words, the plurality offlex sensors are capable of detecting a location on the flexible displaydevice 100 that is being bent by a user's flex input. In addition, theplurality of flex sensors may measure a bending degree to which theflexible display device 100 is bent by a user's flex input and alsocalculate a time period during which a user's flex input bending on theflexible display device 100 is recognized. It should be understood thatall measurement information taken by the sensor unit 150 may beconverted to an electronic signal prior to a transmission to the systemcontroller 110. The system controller 110 may then receive themeasurement information from the sensor unit 150 and control the variouscomponents of the flexible display device 100 accordingly.

According to some embodiments of the present invention, the flex sensorsof the sensor unit 150 may be implemented as pressure detecting sensorsplaced throughout the flexible display device 100. For example thepressure detecting sensors may be a piezoelectric pressure detectingsensors. When a user initiates a flexing of the flexible display device100, this flex input will result in a bend at a location of the flexibledisplay device 100 that coincides with at least one pressure detectingsensor. The pressure detecting sensor at this bend location is thenactivated and proceeds to measure a degree of pressure impacted at thebend location. In most instances the resulting bend on the flexibledisplay device 100 due to a flex input will coincide with more than asingle pressure detecting sensor, and thus a plurality of pressuredetecting sensors will likely be activated for any given flex input. Inthis way, the sensor unit 150 is able to detect locations on theflexible display device 100 that are bent due to a user's flex input.

When information indicating the activation of pressure detecting sensorsis transmitted from the sensor unit 150 to the system controller 110,the system controller 110 is able to recognize that a flex input isbeing performed. The pressure measurements taken by the pressuredetecting sensors that are activated due to a user's flex input aretransmitted to the system controller in real-time. The pressuremeasurements received by the system controller 110 may then beinterpreted by the system controller 110 as representing an angulardegree of bend in the flexible display device 100. For instance, if thesystem controller 110 receives a low pressure measurement from apressure detecting sensor located at a first location of the flexibledisplay device 100, the system controller 110 may interpret the lowpressure measurement as there being a low degree of angular bend on theflexible display device 100 at the first location. Similarly, if thesystem controller 110 receives a high pressure measurement from apressure detecting sensor located at a second location of the flexibledisplay device 100, the system controller 110 may interpret the highpressure measurement as there being a high degree of angular bend in theflexible display device 100 at the second location.

To operate in this way, a given pressure measurement taken by a pressuredetecting sensor may be associated to a given degree of angular bend.Information assigning measured pressure levels to interpreted degrees ofbending on the flexible display device 100 may be stored in the storageunit 120. The list may be a pre-stored list or downloaded onto thestorage unit 120 from an external source via the communications unit130. The list may also be updateable at a later time via thecommunications unit 130 or user.

According to some embodiments of the present invention, the flex sensorsmay alternatively be implemented as tension detecting sensors placedthroughout the flexible display device 100. For example the tensiondetecting sensors may be piezoelectric tension detecting sensors. When auser initiates a flexing of the flexible display device 100, this flexinput will result in a bend at a location of the flexible display device100 that coincides with at least one tension detecting sensor. Thetension detecting sensor at this bend location is then activated andproceeds to measure a degree of tension stress impacted at the bendlocation.

In most instances the resulting bend on the flexible display device 100due to a flex input will coincide with more than one tension detectingsensor, and thus a plurality of tension detecting sensors will likely beactivated for any given flex input.

In addition, a tension detecting sensor according to the presentinvention may be configured to be capable of detecting a user's flexinput that bends a flexible display device in more than one direction.For instance at any given location there may a pair of tension detectingsensors that are placed in a stacked orientation having a top tensiondetecting sensor and a bottom tension detecting sensor. In this way, fora first bend on the flexible display device 100 in a first direction,the top tension detecting sensor may detect a stress caused by a pullingon the top tension detecting sensor, and the bottom tension detectingsensor may detect a stress caused by a condensing on the bottom tensiondetecting sensor. It follows then that for a second bend on the sameflexible display device 100 in a second direction (where the seconddirection is opposite the first direction), the top tension detectingsensor may detect a stress caused by a condensing on the top tensiondetecting sensor, and the bottom tension detecting sensor may detect astress caused by a pulling on the bottom tension detecting sensor.

As mentioned earlier for the cases where the flex sensors areimplemented as pressure detecting sensors, a given tension stressmeasurement taken by a tension detecting sensor may be associated to agiven degree of angular bend on the flexible display device 100.Information assigning measured tension levels to interpreted degrees ofbending on the flexible display device 100 may be stored in the storageunit 120. The list may be a pre-stored list or downloaded onto thestorage unit 120 from an external source via the communications unit130. The list may also be updateable at a later time via thecommunications unit 130 or user.

In an alternative embodiment of the present invention, the flex sensorsmay alternatively be implemented as current detecting sensors placedthroughout the flexible display device 100. The current detectingsensors are able to measure varying degrees of bending on the flexibledisplay device 100 by allowing an electric current to flow through eachcurrent detecting sensor placed throughout the flexible display device100. Then when a user initiates a flexing of the flexible display device100, the current detecting sensors are able to identify changes incurrent and correlate the changes in current as degrees of angularbending on the flexible display device 100.

For example, a current detecting sensor may detect a change in currentrunning through it and transmit such information to the systemcontroller 110. The system controller 110 is then able to identify thelocation of the current detecting sensor that detected a change incurrent, and recognize that the flexible display device 100 is beingbent at that location. Also by calculating the amount of current changedetected by a current detecting sensor, the system controller 110 isable to calculate a degree of bend impacted on the flexible displaydevice 100 due to a user's flex input.

A change in current may be calculated by referencing a current that runsthrough a current detecting sensor in a default state. An example of adefault state may be where the flexible display device 100 lays flat andno flex input is being performed on the flexible display device 100.Consequently the current detecting sensors will detect a natural currentvalue flowing through the current detecting sensors in the defaultstate, and the natural current value may be observed by the systemcontroller 110 and stored in the storage unit 120.

Then during the performance of a flex input by a user, the bending ofthe flexible display device 100 will result in at least one currentdetecting sensor to be bent along a bend line. The bending of thecurrent detecting sensor will fundamentally change an innate electricalprofile of the current detecting sensor when compared to the defaultstate. For instance the resistance characteristic of the currentdetecting sensor may be altered depending upon the degree of bendingimpacted on the current detecting sensor during the performance of theflex input. So as the degree of bending fluctuates during theperformance of the flex input by a user, so too will the resistancecharacteristic of the current detecting sensor fluctuate, and ultimatelythis will cause the current flowing through the current detecting sensorto fluctuate correspondingly. In this case, the physical bending of thecurrent detecting sensor will alter an innate resistance characteristicof the current detecting sensor and this in turn will correspondinglyfluctuate the current flowing through the current detecting sensor.

As mentioned earlier for the cases where the flex sensors areimplemented as pressure detecting sensors, a given change of currentmeasurement taken by a current detecting sensor may be associated to agiven degree of angular bend on the flexible display device 100.Information assigning measured current change levels to interpreteddegrees of bending on the flexible display device 100 may be stored inthe storage unit 120. The list may be a pre-stored list or downloadedonto the storage unit 120 from an external source via the communicationsunit 130. The list may also be updateable at a later time via thecommunications unit 130 or user.

The audio I/O unit 160 illustrated in FIG. 1 may include a speaker orheadphone interface for outputting audio signals originating from thestorage unit 120 of the flexible display device 100. The audio I/O unit160 may also include a microphone for inputting audio signals into theflexible display device 100. Audio signals that are inputted to theflexible display device 100 through the microphone may be transmitted tothe system controller 110 for processing.

The power unit 170 illustrated in FIG. 1 is a power source for providingthe power to operate the various components/units of the flexibledisplay device 100. The power unit 170 may include a battery or aninterface for providing power from external power sources (e.g. directcurrent adaptor, alternating current adaptor).

According to some embodiments of the present invention, certain units ofthe flexible display device 100 may not share the physicalcharacteristic of being flexible, or may only be capable of a low degreeof flexibility. For instance the components that make up the power unit170 and the audio I/O unit 160 may not share the same degree offlexibility as the flexible display unit 140. In such a case, thepresent invention allows for placing certain units of the flexibledisplay device 100 in a dedicated area of the flexible display device100 that does not need to be fully flexible. For instance, units of theflexible display device 100 that have a low flexibility characteristicmay be gathered within a bottom area, top area, middle area orperipheral area of the flexible display device 100. In any case, certainunits of the flexible display device 100 may be gathered within adedicated area of the flexible display device 100, where the dedicatedarea may have a lower flexibility than other areas of the flexibledisplay device 100. Further, in some embodiments of the presentinvention the flexible display device 100 may be configured such thatthe dedicated area may not be intended to be bent for inputting a user'sflex input command.

FIG. 2 illustrates an example for a first bend line 101-2 resulting onthe flexible display device 100 due to the performance of a flex inputby a user, according to some embodiments of the present invention. Thebend line 101-2 illustrated in FIG. 2 is a vertical bend line runningthe portrait length of the flexible display device 100. According tothis first example, the flex input causes the front side of the flexibledisplay device 100 to bend inward in a concave shape centered on thebend line 101-2. FIG. 2 is a front side view of the flexible displaydevice 100, where the front side view is distinguishable for including aflexible display.

A visual cue 102 is illustrated in FIG. 2 to demonstrate, at least, theplacement of a front side flexible display on the flexible displaydevice 100. During the performance of the flex input illustrated by FIG.2, or just prior to the initiation of the flex input, the visual cue 102is displayed on the front side of the flexible display device 100. Thenduring the performance of the flex input, the display of the visual cue102 may be adaptively modified in response to the changing degree ofbending on the flexible display device 100 caused by the flex input.

FIG. 3 illustrates an example for a second bend line 101-1 resulting onthe flexible display device 100 due to the performance of a flex inputby a user, according to some embodiments of the present invention. Thebend line 101-1 illustrated in FIG. 3 is a vertical bend line runningthe portrait length of the flexible display device 100. According tothis second example, the flex input causes the front side of theflexible display device 100 to bend outward in a convex shape centeredon the bend line 101-1. FIG. 3 is a front side view of the flexibledisplay device 100, where the front side view is distinguishable forincluding a flexible display.

A visual cue 103 is illustrated in FIG. 3 to demonstrate, at least, theplacement of a front side flexible display on the flexible displaydevice 100. During the performance of the flex input illustrated by FIG.3, or just prior to the initiation of the flex input, the visual cue 103is displayed on the front side of the flexible display device 100. Thenduring the performance of the flex input, the display of the visual cue103 may be adaptively modified in response to the changing degree ofbending on the flexible display device 100 caused by the flex input.

The flex inputs depicted in FIG. 2 and FIG. 3 describe flex inputs thatbend a flexible display device according to some embodiments of thepresent invention. However the flex inputs described in FIG. 2 and FIG.3 should not be interpreted as being limiting in nature. The flex inputsdescribed by FIG. 2 and FIG. 3 are exemplary in nature and it should beunderstood that it is within the scope of the present invention to allowfor flex inputs that bend the flexible display device of the presentinvention in a variety of different directions and ways. For instance aflex input may only bend a corner of a flexible display device accordingto some embodiments of the present invention.

In any case, no matter the type of flex input that is made on a flexibledisplay device of the present invention, it is an important objective ofthe present invention to accurately recognize a bending on the flexibledisplay device as a valid flex input made by a user. This is animportant feature of the present invention because not all bends of aflexible display device may be intended by a user to be a flex inputcommand. For instance, if a flexible display device is kept in theuser's pocket, it is foreseeable that slight bends in the flexibledisplay device will occur as the user moves around. However these slightbends are not intended by a user to be valid flex input commands, andaccordingly, they should not be recognized as valid flex input commands.Therefore, the flexible display device should be configured to ignoresuch slight bends in the flexible display device and have a mechanismfor distinguishing valid flex inputs as intended by a user, fromunintentional slight bends on a flexible display device.

To accomplish this task, the present invention introduces theimplementation of error buffers when measuring the bend of a user's flexinput on a flexible display device. To better describe the errorbuffers, FIG. 4 illustrates a graph that plots a measured degree ofbending (y-axis) versus time (x-axis). The graph is intended torepresent a measured degree of bending on a flexible display deviceduring the implementation of a user's flex input 410.

When a user first initiates the flex input 410 by beginning to bend theflexible display device, a valid flex input is not immediatelyrecognized. Instead, the flex input 410 will not be recognized as avalid flex input until a measured degree of bending surpasses an errorthreshold value. This is the initial error buffer, and may be referredto as the error threshold value, where in this case the error thresholdvalue corresponds to the first bending value b₁. On the graph, the pointat which the flex input 410 surpasses the error threshold value is seento be located at (t₁, b₁). Although the error threshold value is seen tooccur at time t₁, the error threshold value is not necessarily timedependent. Instead, the error threshold value may be a predeterminedvalue that identifies a measured degree of bending where all measureddegrees of bending that are less than the error threshold value are notto be recognized as a valid flex input. So the error threshold valueserves to disregard slight degrees of bend on the flexible displaydevice that may occur unintentionally.

As the user's flex input 410 continues to bend the flexible displaydevice, eventually the measured degree of bending detected on theflexible display device is seen to surpass the error threshold value at(t₁, b₁), where b₁ corresponds to the error threshold value. Thenstarting from the time, t₁, when the measured degree of bendingsurpasses the error threshold value, the flexible display device willbegin to acknowledge and calculate the flex input 410 as a valid flexinput.

Later during the course of the user's flex input 410, there will come atime where the user will cease bending the flexible display devicefurther, and instead begin to let up on the flexible display device.This scenario correlates to the apex point on the flex input 410 graphof FIG. 4, and may otherwise be referred to as the release point (t₂,b₂). Although preferably the release point value, in this case thesecond bending value b₂, will coincide with a maximum degree of bendingthat is allowed on the flexible display device, according to someembodiments this does not need to be the case. Thus the release pointvalue may correspond to the maximum degree of bending that is allowed onthe flexible display device, or according to other embodiments therelease point value may generally be the point at which the measureddegree of bending on the flexible display device is detected to ceaseincreasing and begin decreasing.

At the release point (t₂, b₂) when the measured degree of bending forthe corresponding flex input 410 is at its maximum, the flexible displaydevice does not immediately end the calculation for the valid flex inputrelated to the user's flex input 410. Instead the flexible displaydevice will wait until the measured degree of bending has reached arelease threshold value. This is considered to be a backend errorbuffer, wherein in this case the release threshold value correlates tothe third bending value b₃. On the graph, the flex input 410 is seen toreach the release threshold value at point (t₃, b₃). So according to thepresent invention, the recognition and calculation for the valid flexinput related to the user's flex input 410 is not stopped immediately atthe first instance of a decrease in the measured degree of bending. Thisis done as a precaution against unintended fluctuations in a user's flexinput.

The actual release threshold value may be based on the release pointvalue. Specifically, the release threshold value may be based on apercentage of the release point value. For instance, the releasethreshold value may be predetermined to be 90% of the release pointvalue. Or put another way, the release threshold value that indicatesthe end of a valid flex input may be based on a 10% decrease in themeasured degree of bending from the measured degree of bending detectedat the release point. So in this case, the release threshold value thatcorrelates to the third bending value b₃ may be 90% of the release pointvalue that correlates to the second bending value b₂.

Alternatively, the release threshold value may be a predetermined numberof units less than the release point value. For instance the releasethreshold value that correlates to the third bending value b₃ may be tenunits less than the measured degree of bending detected at the releasepoint that correlates to the second bending value b₂.

Alternatively, the release threshold value that indicates the end of aflex input may be based on the error threshold value. So in this case,the release threshold value that correlates to the third bending valueb₃ may be equal to the error threshold value that correlates to thefirst bending value b₁. In some embodiments the release threshold valuemay be slightly less than or slightly more than the error thresholdvalue (e.g. 10% less or 10% more).

Alternatively, the release threshold value may be a predetermined numberof units more or less than the error threshold value. For instance therelease threshold value that correlates to the third bending value b₃may be five units more or less than the error threshold value thatcorrelates to the first bending value b₁.

In this way, a valid flex input based on the user's flex input 410 isseen to end, or stop being recognized, after the measured degree ofbending falls beneath the release threshold value. Put another way, theuser's flex input 410 will be recognized as a valid flex input from thetime the measured degree of bending surpasses the error threshold valueto the time the measured degree of bending falls below the releasethreshold value. In this case, the detected bending time for a validflex input resulting from the user's flex input 410 is seen to last fromtime t₁ to time t₃.

FIG. 5 illustrates a graph that plots a measured degree of bending(y-axis) on a flexible display device against time (x-axis) according tothe present invention. Multiple graphs are provided for representing auser's first flex input 510, second flex input 520 and third flex input530. Each of the graphs representing a user's first flex input 510,second flex input 520 and third flex input 530 are provided forexemplary purposes to represent various flex inputs that reach variousmaximum measured degrees of bending b₁, b₂ and b₃ respectively. Each ofthe first flex input 510, second flex input 520 and third flex input 530may begin to be recognized as a valid flex input at the point during thecourse of the respective flex input where the measured degree of bendingsurpasses an error threshold value b_(e). Then after being recognized asa valid flex input, each respective valid flex input will last until themeasured degree of bending falls below a release threshold value b_(r).So a valid flex input corresponding to each of the first flex input 510,second flex input 520 and third flex input 530 may be recognized andcalculated to last from the time each respective flex input surpassesthe error threshold value b_(e) to the time each respective flex inputfalls below the release threshold value b_(r).

Now although the release threshold value b_(r) is depicted in FIG. 5 assharing the same value as the error threshold value b_(e), any of theabove mentioned methods for determining the release threshold value maybe implemented. Therefore, if the release threshold value b_(r) is notsimply set to be equal to the error threshold value b_(e), then each ofthe each of the first flex input 510, second flex input 520 and thirdflex input 530 may each have different corresponding release thresholdvalues. For instance, if the release threshold value b_(r) is set to betied to a maximum measured degree of bending detected for eachrespective flex input, then each of the first flex input 510, secondflex input 520 and third flex input 530 may have differing releasethreshold values assigned to them as they each have differing maximummeasured degrees of bending.

The present invention also envisions methods for recognizing a doubleflex input made by a user on the flexible display device. Therecognition of a double flex input is similar to the recognition of asingle valid flex input described above, with the added requirement thatthe two back to back valid flex inputs must be accomplished within apredetermined time limit. A double flex input that is recognized by theflexible display device may initiate a function that is unique from anyfunction that is initiated by any single valid flex input. The methodfor recognizing a valid double flex input that is distinguishable fromthe succession of two valid flex inputs is described as follows.

FIG. 6 illustrates a graph that depicts a valid double flex input thatmay be recognized by a flexible display device of the present invention.A user's double flex input 610 is actually comprised of a first flexinput and a second flex input that follows successively. The first flexinput of the double flex input 610 is generally represented by the firstcurve (i.e. t₀-t₄), and the second flex input of the double flex input610 is generally represented by the second curve (i.e. t₄-t₈).

The first flex input of the double flex input 610 begins much like theflex input described for FIG. 4. Up until the measured degree of bendsurpasses a first error threshold value the first flex input is notrecognized by the flexible display device as a first valid flex input.This initial degree of bending is discarded as part of the initial errorbuffer. It is not until the measured degree of bending of the user'sfirst flex input surpasses the first error threshold value that theflexible display device will begin to recognize a first valid flexinput. In this case the first error threshold value is represented bythe first bending value b₁. And on the graph provided by FIG. 6 themeasured degree of bending detected from the user's first flex input isseen to surpass the first error threshold value at the point (t₁, b₁).So starting from point (t₁, b₁) the flexible display device will beginto recognize and calculate a first valid flex input.

Release point 1 is then the point at which the measured degree ofbending on the flexible display device due to the user's first flexinput is found to cease increasing and begin decreasing. In the graphprovided by FIG. 6 this release point 1 is represented by point (t₂,b₂). As in the previous description, the recognition and calculation ofthe first valid flex input is not immediately stopped at the firstinstance where the measured degree of bending is found to ceaseincreasing and begin decreasing (e.g. in this case release point 1).Instead, a backend error buffer in the form of a first release thresholdvalue is offered. The first release threshold value is the value atwhich the measured degree of bending due to the first flex input mustfall below before an end to the first valid flex input is recognized. Inthis case the first valid flex input will cease to be recognized andcalculated after the measured degree of bending falls below the firstrelease threshold value represented by the third bending value b₃. Theactual methods for determining the value of the first release thresholdvalue may follow any one of the methods described throughout thisdescription.

In this way the first valid flex input is seen to last from the time themeasured degree of bending surpasses the first error threshold value, tothe time the measured degree of bending falls below the first releasethreshold value. According to FIG. 6, then, the first valid flex inputis detected to last from t₁ to t₃.

Following the end of the first valid flex input at t₃, the user maycontinue to release the bend on the flexible display device. This isrepresented by the measured degree of bending continuing to fall from t₃to t₄ following the end of the first valid flex input at t₃. Then attime t₄ the user's flex input is seen to once again increase a bend onthe flexible display device as evidenced by the increasing slope of thegraph in FIG. 6. The increasing slope starting from time t₄ represents arenewed increasing measured degree of bending. Therefore the second flexinput may be understood as starting at time t₄.

Now similar to how the first flex input only begins to be recognized asa first valid flex input after surpassing the first error thresholdvalue, the second flex input may only begin to be recognized andcalculated as a second valid flex input after surpassing a second errorthreshold value. A second initial error buffer is therefore seen to runfrom time t₄ to t₅ where the second flex input has not yet surpassed thesecond error threshold value, as represented by a fifth bending valueb₅.

The measured degree of bending that constitutes the second errorthreshold value may be based on the first error threshold value. Forinstance the second error threshold value may be equal to the firsterror threshold value. Alternatively, the second error threshold valuemay be assigned to be a percentage more or less of the first errorthreshold value (e.g. 10% more or less than the first error thresholdvalue). Or the second error threshold value may be assigned to be apredetermined number of units more or less than the first errorthreshold value (e.g. 10 units more or less than the first errorthreshold value).

Or alternatively, the second error threshold value may be based on themeasured degree of bending at the point where the second flex inputbegins. In this case this is the fourth degree of bending b₄, where theuser ceases to release the first flex input and resumes bending theflexible display device as the initiation of the second flex input. Forinstance the second error threshold value may be assigned to be apercentage more than the measured degree of bending at the point wherethe second flex input begins (e.g. 10% more than b₄). Or the seconderror threshold value may be assigned to be a predetermined number ofunits more than the measured degree of bending at the point where thesecond flex input begins (e.g. 10 units greater than b₄).

In any case, once the measured degree of bending due to the second flexinput surpasses the second error threshold value, the second valid flexinput will begin to be recognized and calculated. In this case, thesecond valid flex input will begin to be recognized and calculated oncethe measured degree of bending surpasses the second release thresholdvalue corresponding to the fifth bending value b₅.

Then the user may continue to bend the flexible display device as thesecond valid flex input until release point 2 represented by point (t₆,b₆). Release point 2 is where the second flex input ceases increasingand begins decreasing. In other words, the user is seen to beginreleasing the second flex input at release point 2. At this point asecond backend error buffer will be initiated. The second backend errorbuffer will last from time t₆ corresponding to release point 2, to thetime the measured degree of bending due to the second flex input fallsbelow a second release threshold value at time t₇. In this case, thesecond release threshold value in FIG. 6 is represented by the seventhbending value b₇.

The second release threshold value may be based on the first releasethreshold value. For instance, the second release threshold value may beequal to the first release threshold value. Or the second releasethreshold value may be a percentage more or less than the first releasethreshold value (e.g. 10% more or less than the first release thresholdvalue). Or the second release threshold value may be a predeterminednumber of units more or less than the first release threshold value(e.g. 10 units more or less than the first release threshold value).

Or alternatively, the second release threshold value may be based on themeasured degree of bending at release point 2. For instance the secondrelease threshold value may be a percentage less than the measureddegree of bending at release point 2 (e.g. 10% less than the measureddegree of bending at release point 2). Or the second release thresholdvalue may be a predetermined number of units less than the measureddegree of bending at release point 2 (e.g. 10 units less than themeasured degree of bending at release point 2).

In any case, the second valid flex input is seen to end after fallingbelow the second release threshold value, which in FIG. 6 is representedby the seventh bending value b₇. So the second valid flex input lastsfrom time t₅ to t₇.

The essential requirement for a user to successfully accomplish a validdouble flex input is to have the second valid flex input follow within apredetermined amount of time of the first valid flex input. According tosome embodiments, this may require that a second valid flex input mustbegin to be recognized within a predetermined time following therecognized end of a first valid flex input. In other words, a validdouble flex input may be recognized if a second flex input surpasses asecond error threshold value within a predetermined amount of timefollowing a first valid flex input falling below a first releasethreshold value. In the graph illustrated by FIG. 6 this translates tothe time between t₃ and t₅ being less than, or alternatively less thanor equal to, a predetermined amount of time (e.g. 1 second).

Alternatively, according to some embodiments a valid double flex inputmay require that a second valid flex input be recognized to end within apredetermined time following the recognized end of a first valid flexinput. In other words, a valid double flex input may be recognized if asecond valid flex input falls below a second release threshold valuewithin a predetermined amount of time following a first valid flex inputfalling below a first release threshold value. In the graph illustratedby FIG. 6 this translates to the time between t₃ and t₇ being less than,or alternatively less than or equal to, a predetermined amount of time(e.g. 1 second).

While the above example for the recognition of a valid double flex inputhas been described as requiring the detection of a first error thresholdvalue, first release threshold value, point of releasing a first flexinput to initiating a second flex input (e.g. (t₄, b₄) on the graph ofFIG. 6), a second error threshold value and a second release thresholdvalue, other embodiments of the present invention may not require thedetection of as many degree of bending points.

In a simplified method for recognizing a valid double flex input only afirst error threshold value point, a point of releasing a first flexinput to initiating a second flex input (e.g. (t₄, b₄) on the graph ofFIG. 6) and a second error threshold value point may be required to bedetected in order to recognize a valid double flex input. According tothis simplified method, a user may initiate a first flex input on aflexible display device by beginning to bend the flexible displaydevice. Then as a first measured degree of bending is detected due tothe user's first flex input, the first measured degree of bending iscontinuously compared against a first error threshold value. This firsterror threshold value may also be represented by the first bending valueb₁ illustrated in FIG. 6. Now while the first measured degree of bendingis detected to be below the first error threshold value a first validflex input is not recognized.

Later, when the measured first degree of bending is detected to havesurpassed the first error threshold value, a first valid flex input isrecognized. However, unlike the previously described method forrecognizing a valid double flex input, this simplified method does notlook to detect when the measured first degree of bending falls below arelease threshold value. Instead, following the detection of themeasured first degree of bending surpassing the first error thresholdvalue as represented to occur at point (t₁, b₁) on FIG. 6, the nextpoint to be detected is the point at which the release of the first flexinput transitions to an initiation of a second flex input. On FIG. 6this point where the release of the first flex input transitions to aninitiation of a second flex input is represented by point (t₄, b₄). Thedetection of this transition point is important in order to recognizethat a second flex input is being made on the flexible display device.

The transition point (t₄, b₄) can be thought of as essentially are-bending on the flexible display device following the release of thefirst flex input. So following the detection of this transition point, ameasured second degree of bending may be made due to a second flexinput. Then the measured second degree of bending is continuouslymeasured until it is detected that the measured second degree of bendingsurpasses a second error threshold value. The second error thresholdvalue may be represented by the fifth bending value b₅ in FIG. 6.

In order to determine whether a valid double flex input has beenaccomplished according to this simplified method, the time between thedetection of the measured first degree of bending surpassing the firsterror threshold value and the detection of the measured second degree ofbending surpassing the second error threshold value is calculated. Thistime is represented in FIG. 6 as the time between t₁ and t₅. If thistime is less than, or alternatively less than or equal to, apredetermined amount of time then a valid double flex input may berecognized according to this simplified method of the present invention.

It should be noted that the second error threshold value according tothe simplified method may be determined according to any of the methodsdescribed throughout this description.

In any case, for a valid double flex input to be recognized it isimportant that a second flex input is required to follow a first flexinput within a fairly short amount of time. This is to ensure that auser's intention to input a valid double flex input may bedistinguishable from a user's intention to input two separate flexinputs. This is important because a double flex input may take on aunique significance in and of itself. So allowing a prolonged pause inbetween the two flex inputs of a valid double flex input may overlapwith a user's intention to implement two separate flex inputs.

For example, a valid double flex input may be attributed toaccomplishing a delete file task on the flexible display device, while afirst valid flex input by itself may be attributed to opening the fileand a later valid second flex input may be attributed to closing thefile. In this example, if a valid double flex input were allowed to havea prolonged pause in between the two flex inputs that comprised thevalid double flex input, this may interfere with a user's ability toimplement two separate flex inputs that were not intended to be a validdouble flex input.

FIG. 7 serves to illustrate a situation where the time in between twoflex inputs are too far apart to be recognized as a valid double flexinput. A user's overall flex input is depicted by the user input graph710. From a detection standpoint, the flexible display device will firstrecognize a first valid flex input. Then following the recognized end ofthe first valid flex input, the flexible display device will count thetime until a valid second flex input is recognized. Because there is aprolonged time between the end of the first valid flex input at time t₃and the recognition of the second valid flex input at time t₅, theflexible display device will determine that a valid double flex inputcannot be recognized. Therefore the first valid flex input that runsfrom time t₁ to t₃ and the second valid flex input that runs from timet₅ to t₇ will be recognized as two separate flex input commands and nota single valid double flex input command. This is assuming that the timein between the two valid flex input commands (t₃ to t₅) is greater thana predetermined amount of time.

FIG. 8A is a flowchart describing the steps involved for recognizing auser's first flex input as a valid flex input according to the presentinvention. The recognition process begins with step 801 where a userfirst begins to bend a flexible display device and this bending isdetected as a first bend on the flexible display device. Concurrent tothe detection of the first bend, step 801 indicates that a first degreeof bend on the flexible display device due to the first bend will bemeasured.

Then at step 802 a determination is made as to whether the measuredfirst degree of bend surpasses a first error threshold value. If themeasured first degree of bend surpasses the first error threshold value,then the first bend will begin to be recognized as a first valid flexinput and a timer may begin to count the time for which the first validflex input is recognized. The first degree of bend will also continue tobe measured.

However, if the determination at step 802 finds that the measured firstdegree of bend does not yet surpass the first error threshold value,then the first bend will not yet be recognized as a first valid flexinput. Instead, it may be assumed that the user's first bend willcontinue to increase the bending on the flexible display device, andconsequently the first degree of bend will continue to be measured.

Following the recognition of the first bend as the valid first flexinput at step 803, at step 804 a determination will be made as towhether the measured first degree of bend has fallen below a firstrelease threshold value. If the measured first degree of bend has fallenbelow the first release threshold value, then the process proceeds tostep 805 where an end to the first valid flex input is recognized.

However if the measured first degree of bend has not yet fallen belowthe first release threshold value, an end to the first valid flex inputis not yet recognized. Instead, the process returns to step 803 wherethe flexible display device will continue to recognize the first validflex input and continue to count the time of the first valid flex input.

Following the recognized end of the first valid flex input, the flexibledisplay device may implement a function or operation on the flexibledisplay device that corresponds to the recognized first valid flex inputcommand. However, if a user beings to initiate a second bend on theflexible display device, a double flex input may be intended by theuser. Therefore the process will continue to a second set of steps fordetermining whether to recognize a valid double flex input.

FIG. 8B illustrates a flowchart of steps that describe a method forrecognizing a valid double flex input according to some embodiments ofthe present invention. Following the recognized end to the valid firstflex input at step 805, a user may initiate a second bend which isdetected at step 806. Also in step 806, a second degree of bend on theflexible display device due to the detected second bend will begin to bemeasured.

Then at step 807 a determination will be made as to whether the measuredsecond degree of bend surpasses a second error threshold value. If themeasured second degree of bend does surpass the second error thresholdvalue, the second bend will be recognized as the start of a second validflex input at step 808.

However if the measured second degree of bend does not yet surpass thesecond error threshold value, then the process returns to measuring thesecond degree of bend on the flexible display device due to the secondbend at step 806.

Now assuming that the second bend has been recognized as a second validflex input at step 808, the process proceeds to step 809 where adetermination is made as to whether the second valid flex input wasrecognized within a predetermined amount of time from the end of thefirst valid flex input. If it is determined that the second valid flexinput began to be recognized as a valid flex input within thepredetermined amount of time following the end of the first valid flexinput, then a valid double flex input is recognized as depicted by step810. In this case as illustrated in FIG. 6, the time in-between the endof the first valid flex input and the start of the second valid flexinput being recognized is the time from t₃ and t₅.

However if it is determined that the second valid flex input was notinitially recognized as a valid flex input within the predeterminedamount of time following the end of the first valid flex input, then avalid double flex input is not to be recognized. Instead, step 811indicates that the second valid flex input is to be recognized as aseparate valid flex input.

So for the method described by the flowchart of FIG. 8B, the flexibledisplay device will measure the time between the recognized end of afirst valid flex input and the recognized beginning of a second validflex input. Then if the time between the recognized end of a first validflex input and the recognized beginning of a second valid flex input isless than a predetermined amount of time, a valid double flex input willbe recognized.

FIG. 8C illustrates a flowchart depicting steps for an alternativemethod of recognizing a valid double flex input according to someembodiments of the present invention. Following the recognized end tothe valid first flex input at step 805, a user may initiate a secondbend which is detected at step 806′. Also in step 806′, a second degreeof bend on the flexible display device due to the detected second bendwill begin to be measured.

Then at step 807′ a determination will be made as to whether themeasured second degree of bend surpasses a second error threshold value.If the measured second degree of bend does surpass the second errorthreshold value, the second bend will be recognized as a second validflex input at step 808′.

However if the measured second degree of bend does not yet surpass thesecond error threshold, then the process returns to measuring the seconddegree of bend on the flexible display device due to the second bend atstep 806′.

Now assuming that the second bend is recognized as a second valid flexinput at step 808′, the process proceeds to step 809′. At step 809′ adetermination is made as to whether the measured second degree of bendhas fallen below a second release threshold value. If the measuredsecond degree of bend has indeed fallen below the second releasethreshold value, then an end to the second valid flex input isrecognized as indicated by step 810′.

However, if the measured second degree of bend has not fallen below thesecond release threshold value, then the process returns to step 808′where the recognized second valid flex input continues to be recognizedand the second degree of bend continues to be measured.

Now assuming that the end of the second valid flex input has beenrecognized at step 810′, the process will proceed to step 811′ where adetermination is made as to whether the end of the second valid flexinput was recognized within a predetermined amount of time from the endof the first valid flex input. If the end of the second valid flex inputis determined to have been recognized within the predetermined amount oftime following the recognized end of the first valid flex input, then avalid double flex input may be recognized as represented by step 812′.In this case as illustrated in FIG. 6, the time in-between the end ofthe first valid flex input and the end of the second valid flex inputbeing recognized is the time from t₃ and t₇.

However if the end of the second valid flex input is determined to nothave been recognized within the predetermined amount of time followingthe recognized end of the first valid flex input, then a valid doubleflex input may not be recognized as represented by step 813′. Instead,step 813 indicates that when the end of the second valid flex input isdetermined to have not been recognized within the predetermined amountof time following the recognized end of the first valid flex input, thesecond bend is simply recognized to be a second valid flex input thatfollows the first valid flex input.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present invention. Thus,although the foregoing description has been described with reference tospecific examples and embodiments, these are not intended to beexhaustive or to limit the invention to only those examples andembodiments specifically described.

What is claimed is:
 1. A method for detecting a bend on a flexible display device, the method comprising: detecting a first bend on the flexible display device and measuring a first degree of the first bend; recognizing the first bend as a first valid flex input when the measured first degree of bend surpasses a first error threshold value; and recognizing an end of the first valid flex input when the measured first degree of bend falls below a first release threshold value, wherein a maximum degree of bend measured during the first bend is recognized as a first peak value, wherein the first error threshold value is determined based on a degree before the flexible display device is bent and the first release threshold value is determined based on the first peak value, and wherein the first release threshold value is different from the first error threshold value.
 2. The method of claim 1, wherein the first error threshold value is determined by adding a predetermined number of units to the degree before the flexible display is bent.
 3. The method of claim 1, wherein the first release threshold value is determined by decreasing a predetermined number of units from the first peak value.
 4. The method of claim 1, wherein the first release threshold value is greater than the first error threshold value.
 5. The method of claim 1, wherein the first release threshold value is equal to a percentage of the first error threshold value.
 6. The method of claim 1, further comprising: detecting a second bend on the flexible display device following the end to the first valid flex input, and measuring a second degree of bend due to the second bend; recognizing the second bend as a second valid flex input when the measured second degree of bend surpasses a second error threshold value, and recognizing an end to the second valid flex input when the measured second degree of bend falls below a second release threshold value.
 7. The method of claim 6, wherein a valid double flex input is recognized if the second valid flex input is recognized within a predetermined time following the end to the first valid flex input.
 8. The method of claim 7, wherein the recognition of the valid double flex input is predetermined to execute a specific function of the flexible display device.
 9. The method of claim 6, wherein a valid double flex input is recognized if the second valid flex input ends within a predetermined time following the end to the first valid flex input.
 10. The method of claim 9, wherein the recognition of the valid double flex input is predetermined to execute a specific function of the flexible display device.
 11. The method of claim 6, wherein the second error threshold value is determined based on a degree at a point where the second bend begins.
 12. The method of claim 6, wherein a maximum degree of bend measured during the second bend is recognized as a second peak value.
 13. The method of claim 12, wherein the second release threshold value is determined based on the second peak value.
 14. The method of claim 6, wherein the second release threshold value is determined by decreasing a predetermined number of units from the second peak value.
 15. A flexible display device having at least one flexible portion, comprising: a display unit configured to display visual information; a sensing unit configured to measure a degree of bend; and a system controller configured to recognize a first bend as a first valid flex input when a first degree of bend surpasses a first error threshold value, and to recognize an end to the first valid flex input when the first degree of bend falls below a first release threshold value, wherein a maximum degree of bend measured during the first bend is recognized as a first peak value, wherein the first error threshold value is determined based on a degree before the flexible display is bent and the first release threshold value is determined based on the first peak value, and wherein the first release threshold value is different from the first error threshold value.
 16. The flexible display device of claim 15, wherein the first error threshold value is determined by adding a predetermined number of units to the degree before the flexible display is bent.
 17. The flexible display device of claim 15, wherein the first release threshold value is determined by decreasing a predetermined number of units from the first peak value.
 18. The flexible display device of claim 15, wherein the first release threshold value is greater than the first error threshold value.
 19. The flexible display device of claim 15, wherein the first release threshold value is equal to a percentage of the first error threshold value.
 20. The flexible display device of claim 15, wherein: the sensing unit is further configured to detect a second bend on the flexible portion following the end to the first valid flex input, and measure a second degree of bend due to the second bend, and the system controller is further configured to recognize the second bend as a second valid flex input when the measured second degree of bend surpasses a second error threshold value, and also recognize an end to the second valid flex input when the measured second degree of bend falls below a second release threshold value.
 21. The method of claim 20, wherein a valid double flex input is recognized if the second valid flex input is recognized within a predetermined time following the end to the first valid flex input.
 22. The method of claim 21, wherein the recognition of the valid double flex input is predetermined to execute a specific function of the flexible display device.
 23. The method of claim 20, wherein a valid double flex input is recognized if the second valid flex input ends within a predetermined time following the end to the first valid flex input.
 24. The method of claim 23, wherein the recognition of the valid double flex input is predetermined to execute a specific function of the flexible display device.
 25. The method of claim 20, wherein the second error threshold value is determined based on a degree at a point where the second bend begins.
 26. The method of claim 20, wherein a maximum degree of bend measured during the second bend is recognized as a second peak value.
 27. The method of claim 20, wherein the second release threshold value is determined based on the second peak value.
 28. The method of claim 20, wherein the second release threshold value is determined by decreasing a predetermined number of units from the second peak value. 